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Precision Engineering Atomic-Scale Measuring Machine Measuring Patterned Layers on Integrated Circuits |
Precision Engineering Division Contact: Dennis Swyt Manufacturers rely on accurate dimensional measurements as one means to assure consumers of the quality and interchangeability of its parts and assemblies. These measurements become more critical as the dimensional tolerances get smaller. U.S. manufacturers need reliable methods for ensuring dimensional precision and accuracy to compete in world markets. This program provides world-class measurements—from a fraction of a millimeter to more than a meter—and Standard Reference Materials to its customers. Calibrated artifacts provide a very direct path of traceability of industry measurements to the international standard of length and are used as measurement reference standards to ensure that the dimensions of manufactured parts meet their design specifications. When manufactured parts conform to their design specifications—and such conformance is verified by traceable measurements—they work better and last longer. They also can be properly assembled with parts manufactured at other companies throughout the nation and the world, and can meet requirements for international trade. NIST annually calibrates more than 5,000 dimensional artifacts for more than 160 organizations in 40 states. NIST calibrations are the keystone in assuring traceable measurements for the U.S. discrete-parts manufacturing sector; they establish a direct, straightforward, and convincing path of traceability to international standards. Developing new measurement techniques and, thus, improving our own measuring capabilities will have direct economic benefits for our customers, allowing manufacturers to explore areas of design and development previously unapproachable due to measurement limitations. For example, improvements in our ability to measure small holes or small structures will impact the performance of optical networks, fuel injectors, magnetic storage technology, and high-frequency microwave systems. Contact: Ted Doiron U.S. manufacturers of large-scale objects must now compete in a global market by cooperating with second tier suppliers--buying some components from one company and other components from another company. The components then are assembled into complex multi-dimensional objects. In addition, large-part manufacturing also must contend with ever-decreasing tolerances, driven by the desire to reduce dimensional variation, enhance performance, and promote greater interchangeability. The larger a manufactured object is, the more important dimensional variation and interchangeability become to product performance. For example, in the recent past, more than a ton of shims were needed to assemble a large commercial aircraft to compensate for the dimensional variations in individual components. This shim weight (1 ton), even today, adds approximately $1 million annually per plane in unnecessary operating costs. Traditional manufacturers (i.e., Boeing, Caterpillar, DaimlerChrysler, and Ford), and their suppliers increasingly desire the ability to measure large-scale objects (those 1 meter or larger) with uncertainties approaching a few micrometers. And because of a multi-tier approach to manufacturing, the measurements of their suppliers must demonstrate traceability to the international standard of length and be accompanied by measurement uncertainty statements. In addition to traditional manufacturers, the ship building industry and other organizations including NASA; atomic accelerator sites, such as Brookhaven, Fermilab, and Stanford Linear Accelerator; and large Earth-based telescopes need accurate large-scale measurements. They employ large-scale metrology techniques to establish and maintain the critical alignment of their systems. Large-scale manufacturers rely on a cadre of three-dimensional coordinate measuring systems such as coordinate measuring machines, theodolites, laser trackers, photogrammetry, and 3-D scanners to measure their objects. Therefore, standards, calibrations, and measurement methods for these systems continue to be a high priority for them. These priorities are supported by the efforts of the scientists and engineers in NIST's Large-Scale Metrology program. Through these efforts, U.S. large-scale manufacturing metrologists will have the necessary tools--standards, artifacts, and methodology, including mathematical modeling--to characterize the instruments. Examples are standards developed through American Society of Mechanical Engineers B89 Dimensional Metrology Committee, artifacts through calibration research, and methodology through research and the Algorithm Testing Project. The goal behind these tools is to provide manufacturing metrologists the ability to reduce calibration time, increase the time between calibrations, and establish traceability of measurements, all of which can increase their companies' competitiveness. Contact: Charles J. Fronczek Semiconductor, flat-panel display, and high-density memory manufacturing industries need measurement methods and artifacts whose dimensions are known with nanometer-scale accuracy. NIST's Nanometer Scale Metrology program develops length-intensive measurement capabilities and calibration standards in the nanometer-scale regime. The program's scientists work on issues aimed at accurate nanometer-length metrology through scanning probe microscopies, optical microscopy, interferometry, scanning electron microscopy, and traditional linescale interferometry. Remarkably, according to Moore's Law, the number of transistors that can fit on a microchip will double every 18 to 24 months. This has held true for many years. However, keeping up with this famous prediction by Intel founder Gordon Moore is becoming more difficult. As chip makers approach the limits of current semiconductor materials, NIST works with electronics manufacturers to develop new technologies, processes, measurement methods, and standards and to steadily improve enabling technologies, including optical systems, resists, etch systems, and metrology. New measurement methods and standards will improve measurement accuracy and repeatability, thus facillitating the continued shrinkage of integrated-circuit features. The semiconductor industry presents the most-demanding metrology needs. Solutions to these advanced needs then can be transferred to other industries. The International Technology Roadmap for Semiconductors sets aggressive technical goals for the semiconductor industry and, by extension, the NIST Nanoscale Metrology Program. Since the program's inception, critical dimension and overlay metrology, two areas identified in the industry roadmap, have been strengths. Improvements in metrology equipment and methods have the potential to yield large savings for manufacturers. For example, a Charles River Associates study of the impacts of the NIST photomask linewidth standard estimated industry savings to total $30 million. Since the study, the 2001 photomask market has more than quintupled. Over the same span, NIST has introduced a series of photomask linewidth standards and a new one is in preparation. Contact: Michael T. Postek Atomic-Scale
Measuring Machine In one demonstration of its capabilities, M-cubed imaged, with nanometer-scale resolution, an array of chromium lines over a 5-micrometer by 1-millimeter area. Analysis of the image data yielded an average line spacing of 212.69 nanometers. The estimated standard uncertainty for the measurement was of 0.03 nanometer, which is about one-tenth the distance of typical interatomic spacings. In another measurement, the atomic-resolution scanning probe was able to track continuously a grating surface for 10 millimeters, counting out 49,996 lines and measuring an average line spacing of 200.011 nanometers. This grating now is being used as a reference standard for an X-ray spectrometer currently used on the Chandra X-ray Observatory built by NASA. M-cubed also will serve as an exploratory tool for building mechanical and electrical structures in the nanometer size range. Among the organizations that have collaborated on the construction of M-cubed are several major universities and national laboratories as well as IBM Watson Research Center, Lucent Technologies, and Zygo Corp. Contact: John Kramar Measuring Patterned Layers on Integrated Circuits NIST researchers develop techniques for measuring the critical dimensions of patterned layers on integrated circuits. Work addresses the theory and practice of image formation with optical, scanning electron, and scanning probe microscopes, all of which are used in semiconductor manufacturing. Researchers also investigate new metrology instruments to calibrate measurement standards. This project was initiated about 25 years ago at the request of the semiconductor industry. Now at about 100 nanometers, critical dimensions for semiconductors will continue to decrease, creating continual demand for new and improved measurement techniques and related standards. For example, the dimensions of NIST optical photomask Standard Reference Materials (SRMs) range from about 30-micrometer to 0.5-micrometer linewidths and, in the future, likely will be extended to even smaller dimensions. For the scanning electron microscope, a semiconductor-based research material (RM 8090) currently is available for SEM magnification calibration with a minimum pitch of 200 nanometers stepping to a maximum pitch of about 3 millimeters. The artifacts for this future SRM currently are being fabricated. RM 8090 (and the future SRM 2090) is useful at both high and low accelerating voltage modes of the instrument. New and improved standards for integrated circuit metrology are the objects of ongoing research. Contact: Michael T. Postek Shop
Floor as a National Measurement Institute Nearly the entire spectrum of U.S. manufacturing, from aircraft and automobiles to semiconductors and disc drives, is contending with technological trends that require ever more advanced measurement capabilities at the level of the shop floor. Traditionally, traceability was confined to measurements of master length standards, housed in a company's calibration laboratory. Today, traceable measurements on commercial components are increasingly necessary to comply with the international product and quality-system standards and accreditation programs. The scientists and engineers involved in the Shop Floor as a National Measurement Institute (SF-NMI) program seek to assist industry in achieving traceability for dimensional measurements. Traceable measurements require a demonstrable connection to the international unit of length and a task-specific measurement uncertainty statement. Sophisticated business customers rely on uncertainty statements to help them determine whether parts and products will consistently meet design specifications and whether features will be within tolerances. One of our goals is to provide information on the connection to the SI unit of length and on how industry can realize the international standard of length without using the calibration services of NIST or another National Measurement Institute. Another is to develop the means by which U.S. manufacturers can quickly and economically meet these traceability requirements for dimensional measurements made on the shop floor. Working with standards-developing organizations such as American National Standards Institute and the American Society of Mechanical Engineers (ANSI/ASME), we plan to deliver standards, guidelines, and technical reports. Currently, we are represented on subcommittees within the ANSI/ASME B89.7 Subcommittee on Measurement Uncertainty in Dimensional Measurements framework. In addition to the standards work, we are pursuing ongoing research and development activities that include: developing calculational methodologies for assessing the uncertainty of coordinate metrology measurements; developing laser-based dimensional metrology instruments; assessing thermal sources of dimensional measurement uncertainty in the industrial environment, and addressing fundamental issues of dimensional metrology calibrations. Contact: Steve Phillips Surface microstructure affects the operation of components in the automobile, aerospace, semiconductor, metals, and optics industries. NIST is developing measurement techniques and standards to benefit all of these manufacturing industries. NIST plays an important role for manufacturers by providing accurate calibration of critical surface features. For the metals industry, NIST developed a new approach to measuring the geometry of Rockwell C hardness indenters, and the method has quickly become the most accurate in the world. Better control of indenter geometry enables improvement in the hardness measurement itself. With this new approach, NIST unified Rockwell C hardness scales worldwide. NIST calibrations support a variety of measurements, including average and root mean square roughness, power spectral density of roughness, hardness indenter radius, and cone angle. For the optics and semiconductor industries, NIST developed a calibrated atomic force microscope, which is calibrated against the wavelength of light in all three coordinate axes. This device calibrates three-dimensional artifacts that, in turn, will be used to calibrate scanning probe microscopes. The semiconductor industry relies on NIST to provide accurate surface measurements of step heights and pitch spacings. For the data storage industry, NIST calibrations support line edge roughness measurements. This program is responsible for certifying Standard Reference Materials for roughness and for calibration of the magnification of scanning electron microscopes. Contact: Theodore
Vorburger
Date
created:December
17, 2001 |